[TowerTalk] 80m dipole with open-sleeve parasitic

[knormoyle at surfnetusa.com]

<I'm going to look at the arrl articles Rick listed>

Jim asked "When you say open sleeve, do you basically mean something where the 
apparent diameter of the conductor is larger (e.g. like cage dipoles, 
bowties, biconicals, and to a lesser extent, fan dipoles)?"

I use "open sleeve" in terms of a second single, parallel parasitic dipole element, shorter than than the dipole 
driven element, and parallel to it, but not one cut for another band. In terms of whether you should call 
it "loading" ..I think not, since it's not physically in the driven element, like normal L we talk about for the 
driven element. I also don't think that the abstraction of saying it's an apparent larger diameter is right.

(next we'll argue about how a folded dipole with 6" separation "acts" ! :)

This definition of "open sleeve" is a reduction of the original dual parallel wires, or coax, incarnations, but 
commonly described with the same words.

Side note: I was reading Tom Schiller's (Force12) patents on open-sleeve feeds for 20/15/10 tribanders.
http://www.freepatentsonline.com/5995061.html

He calls his patent "No loss, multi-band, adaptable antenna"
The "no-loss" might get some eyebrow-raising :)

Curiously, he mentions 1.14x as an interesting minimum frequency delta for the parasitic element. Don't know how 
he came up with that.


"17. A low loss antenna comprising: 
a driven element resonant at a first frequency, not resonant at a second frequency, and not resonant at a third 
frequency; 

a first adjacent element adjacent to the driven element on a first side of the driven element, said first adjacent 
element spaced apart from the driven element and resonant at the second frequency, not resonant at the first 
frequency, and not resonant at the third frequency; and 

a second adjacent element adjacent to the driven element on a second side of the driven element, said second 
adjacent element spaced apart from the driven element and resonant at the third frequency, not resonant at the 
first frequency, and not resonant at the second frequency; and 

a common feed point located at the driven element for coupling to a feedline for feeding signal energy to the 
driven element; 

where the second frequency is at least 1.14 times the first frequency, the third frequency is at least 1.14 times 
the second frequency, and the third frequency is less than two and one-half times the first frequency."


and


"24. The low loss antenna as set forth in claim 17, wherein the electrical length of the first adjacent element is 
at least 14% greater than the electrical length of the second adjacent element."


Now the elements here are fatter, and shorter for a 20/15/10 tribander than what I'm talking about.. So maybe the 
losses aren't as interesting?
Or just part of a tradeoff

-kevin
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